1. Field of the Invention
The present invention relates to a crankcase of an internal combustion engine.
2. Description of Background Art
An internal combustion engine is known that includes a crankcase composed of an upper crankcase half and a lower crankcase half. In this kind of crankcase, the upper crankcase half and the lower crankcase half respectively have an upper journal support wall and a lower journal support wall for cooperatively supporting a crank journal of a crankshaft. The upper journal wall and the lower journal wall are fastened together by a journal bolt mounted from the lower surface of the crankcase. See, for example, Japanese Patent Laid-open No. 2004-308519.
In the above-mentioned internal combustion engine, lubricating oil (engine oil) is supplied from an oil pump to a cylinder portion, for example, and returned from one lateral side of the crankcase to an oil pan located below the crankcase.
However, in the case that the lubricating oil from the one lateral side of the crankcase is passed through a portion of the crankcase laterally outside of the journal support wall and the journal bolt and returned to the oil pan, the width of the oil pan must be increased to cause an increase in size of the oil pan.